This invention relates to radiation curable coating compositions and, more particularly, to the radiation curing of coating compositions which contain filler materials.
Radiation curable coatings, such as inks and films, are of increasing importance because they do not require the use of inert, volatile solvents, which can be objectionable from an environmental protection standpoint. Many radiation curable materials are known, such as liquid monomers and prepolymers or oligomers with ethylenically unsaturated groups which polymerize on exposure to ionizing or actinic radiation. Suitable materials and procedures are described in my prior U.S. Pat. No. 3,989,609.
In the case of compositions which are pigmented or dyed to provide color and opacity, there are often difficulties in radiation curing, especially with actinic radiation of low penetrating power. This is because pigments and additives restrict penetration of the radiation through the base material. The result has been limited use of such materials, the requirement of long exposure times, or the need for using expensive and hazardous ionizing radiation of greater penetrating power.
Accordingly, it is an object of the invention to facilitate the curing of radiation curable coating compositions. A related object is to achieve ready and inexpensive cure even in the presence of filler materials.
Other objects include provision for increased printing and coating speeds with radiation curable materials, and provision of printing plates, indicia, photoresists and the like from partially cured, non-tacky continuous films.